1. Field of the Invention
The present invention relates to a substrate processing apparatus which performs a variety types of surface treatments (e.g., development, etching, cleaning, rinsing, drying) upon a variety types of substrates such as a semiconductor wafer, a glass substrate for photomask, a glass substrate for liquid crystal display, a glass substrate for plasma display and an optical disk substrate (hereinafter simply referred to as “substrates”).
2. Description of the Related Art
A substrate processing apparatus which is shown in FIG. 9, for instance, has been proposed as this type of substrate processing apparatus. Disposed in the illustrated substrate processing apparatus are an indexer 1 and a processing module 2 which is disposed adjacent to and on one side to the indexer 1. The indexer 1 comprises a cassette mounting stage 12 which mounts a plurality of cassettes 11 each capable of housing more than one substrates W, and an indexer robot 14 which can move on an indexer transportation path 13 extending long along a direction Y. The index robot 14 loads the substrates W into and unloads the substrates W out from the cassettes 11. The processing module 2 comprises a main transportation robot 22 which can move on a main transportation path 21 which extends long along a direction X perpendicular to the direction Y, and unit columns 23, 24 which are disposed on the both sides of the main transportation path 21. In the unit columns 23, 24, processing units 231 through 233 and 241 through 243 are respectively arranged in the direction X.
In the substrate processing apparatus having such a structure above, after unloaded by the indexer robot 14, the substrates W housed in the cassettes 11 are handed over to the main transportation robot 22. Receiving the substrates W yet to be processed, the main transportation robot 22 moves to arrive at any one of the processing units 231 through 233 and 241 through 243, and inserts the substrates W to this processing unit. Meanwhile, the processed substrates W are unloaded from this processing unit by the main transportation robot 22 and thereafter transported to the next processing unit.
After such an operation is repeated and a series of processing is performed upon the substrates W, the main transportation robot 22 moves on the main transportation path 21 while still holding the substrates W, and hands over the substrates W to the indexer robot 14. The indexer robot 14 puts the received substrates W into the cassettes 11 which used to originally house these substrates. This structure allows the main transportation robot 22 to access the processing units 231 through 233 and 241 through 243 in any desired order, and therefore, an order in which the processing is to be performed upon the substrates W can be freely set.
By the way, while the sizes of patterns of semiconductor devices have been rapidly reduced over the recent years, these endeavors have led to a new problem to processing of substrates. For instance, when a resist applied on a substrate W is to be patterned in order to create fine patterns, a development process, a rinsing process and a drying process are executed one after another. A developing fluid such as an alkaline solution is used during the development process for developing the resist applied on the substrate W and accordingly removing an unnecessary amount of the resist, a rinsing fluid such as deionized water is used during the rinsing process for removing the developing fluid as it is after the development process, and during the drying process, centrifugal force acts upon the rinsing fluid which remains on the substrate W and the rinsing fluid is removed from the substrate W to dry (spin drying process). During the drying process among these processes, if the interface between the rinsing fluid and a gas appears on the substrate W as drying proceeds and if this interface shows itself in a gap between the fine patterns of the semiconductor device, the surface tension of the rinsing fluid pulls the fine patterns toward each other and accordingly destroys the fine patterns, which is a problem.
A few solutions to this problem have been studied, one of which is to form all or some of the processing units 231 through 233 and 241 through 243 by the apparatus described in Japanese Patent Application Laid-Open Gazette No. H8-250464 (hereinafter referred to as “the proposed apparatus”). The proposed apparatus continuously executes a wet surface treatment, in which a substrate W transported as it is housed in a container is processed within the container a wet surface treatment (wet process) with a liquid-state chemical agent, and a supercritical drying process. The continuous processing is carried out within the same apparatus as described below.
First, the main transportation robot 22 loads the substrates W into the container. After the developing fluid is supplied and a development process is carried out, a rinsing process with deionized water and a substitution process with a substitution fluid containing alcohol are executed in this order as a wet process. Following this, liquid-state carbon dioxide is introduced into the container to substitute alcohol, the temperature is increased after the substitution with liquid-state carbon dioxide to force carbon dioxide into a supercritical state, and the pressure is then reduced, thereby executing supercritical drying. Execution of supercritical drying in this manner prevents destruction of fine patterns.
However, in the event that all or some of the processing units are formed by the proposed apparatus, there are following problems. First, the processing units using a supercritical fluid are under more restricting conditions as compared to frequently used conventional processing units, i.e., processing units which execute surface treatments under an atmospheric pressure. In other words, a corrosive chemical agent, such as strong acid and strong alkali, can not be introduced for execution of surface treatments although a pressure vessel needs be used as the container, and therefore, the range of selection of chemical agents is drastically restricted. This is because a pressure vessel is mainly made of a metallic material considering the resistance against pressure and because strong acid or alkali corrodes a surface of the pressure vessel which is exposed to a chemical fluid. While an obvious solution is to coat an inner surface of the pressure vessel with a corrosion-resistant coat such as a fluorocarbon resin, it is virtually difficult to keep the coating continuously exhibiting this function under a high pressure over a long period of time. Further, even if the inner surface of the pressure vessel is coated with a corrosion-resistant coat, it is very difficult to coat inner surfaces of all parts and components, such as a small pipe, a joint and a high-pressure valve, leading to the inner surface of the pressure vessel with a corrosion-resistant coat.
An approach to solve this problem may be to distinguish a wet surface treatment, which causes a problem in terms of corrosion resistance, from a surface treatment which uses a supercritical fluid. In other words, the former (wet surface treatment) may be executed with the conventional processing units while the latter (supercritical surface treatment) may be executed with processing units which are formed by the proposed apparatus. However, such a structure leads to the following problem.
First, in the substrate processing apparatus shown in FIG. 9, the proposed apparatus is used as some of the processing units of the substrate processing apparatus and a wet surface treatment which causes a problem in terms of corrosion resistance is executed by the conventional processing units. As is clear from FIG. 9, a processing unit for executing the wet surface treatment (hereinafter referred to as a “wet processing unit”) and a processing unit which is formed by the proposed apparatus (hereinafter referred to as a “high-pressure processing unit”) are both disposed facing the main transportation path 21. Therefore, it is necessary for the main transportation robot 22 to transport the substrates W from the wet processing unit to the high-pressure processing unit. In this manner, since the substrates W as they are immediately after treated with the wet surface treatment by the wet processing unit are wet with a processing fluid such as a rinsing fluid and a substitution fluid, the main transportation robot 22 directly touches the substrates W in such a condition. During this wet transportation, a substrate holding portion (not shown) of the main transportation robot 22 therefore gets wet with the processing fluid. As a result, as other dried substrates are held in the substrate holding portion which is thus wet, these substrates get wet once again, which in turn causes a problem that a production yield decreases.
Further, while another approach is to dispose a dedicated transportation robot between the wet processing unit and the high-pressure processing unit, since the both processing units are arranged facing the main transportation path 21, the dedicated transportation robot as well needs inevitably be disposed close to the main indexer transportation path. Hence, during wet transportation of the substrates W by the dedicated transportation robot from the wet processing unit to the high-pressure processing unit, the main transportation robot 22 gets wet or contaminated as the processing fluid or the like adhering to the substrates W splashes around toward the main transportation path 21 or as the processing fluid partially evaporates and accordingly leaks out toward the main transportation path 21, thereby leading to a decrease in production yield in a similar fashion to the above.